This invention relates in general to high pressure liquid chromatography and, more particularly, to an apparatus and process for conducting such chromatography automatically with respect to a plurality of liquid test samples during an extended period of time without the attention of an operator.
Persons familiar with the use and operation of liquid chromatographs have been aware of the need for complete automation thereof. Presently, the injection of test samples is carried out manually by an operator who must be present almost constantly because he must manually inject a new test sample into the chromatograph after the recording of the preceding test sample has been completed. Often the cycle time of each sample is as small as 10 minutes so that it is difficult for the operator to perform any other beneficial duties without compromising the efficient operation of the chromatograph. This arrangement is not only boring for the operator, but also wastes valuable human resources represented by the skill of such an operator.
In the great majority of existing liquid chromatographs, the sample liquid is manually injected into the chromatograph through a septum so that the performance of the chromatograph is dependent to a considerable extent upon the technical skill of the operator who performs the injections. An improper injection can produce an unreliable run or assay which must then be thrown out. While some attempts have been made to overcome the inaccuracies produced by manual injections, as by using a valved injection mechanism, this operation has still required the presence of an operator to actuate the valve at the proper time for each test sample.
Refilling of the liquid phase pump for the chromatograph has heretofore been on demand, namely, when a sensor indicated the pump needed refilling. Often, the filing function occurred during the movement of a test sample through the chromatograph. It has been found that such an occurrence can adversely affect the accuracy of the chromatogram for that test sample.
In the past, liquid chromatographs have not always had a completely foolproof and reliable rinsing function. Thus, the assay from one sample has sometimes been made inaccurate by a carry-over of a preceding test sample.
With existing apparatus for performing high pressure liquid chromatography, it is often necessary to introduce into each test sample a standard having a sufficiently different molecular structure than the material being analyzed that a comparison can be made to determine the concentration of the test material present. However, by using the equipment to be described hereinafter, it is believed that the need for such a standard can be materially reduced because of the greater accuracy procedurewise and timewise with which the injection of the test sample can be effected, and because the virtual elimination of the human error.
Accordingly, a primary object of this invention is the provision of an apparatus including a high pressure liquid chromatograph, for automatically and successively analyzing and recording the ingredients in a plurality of test samples over an extended period of time without the attention of an operator.
A further object of this invention is the provision of an apparatus, as aforesaid, in which a small portion of any given liquid test sample is separated from the remainder of that test sample and injected into the chromatograph at a preselected point in time with reference to the completion of the analysis of the next preceding test sample.
A further object of this invention is the provision of an apparatus, as aforesaid, including a rinse and sample transport system for automatically, and at a preselected point in time with reference to the cycle of analyzing the next preceding test sample, purging the transport system with said rinse and thereafter delivering said other sample to said chromatograph.